Production of polyhydric alcohols



Patented July 5,1938

PRODUCTION OF POLYHYDBIC ALGOHOLS Herbert P. A. Groll and George Hearne,Berkeley, OaliL, assignors to Shell Development Company, San Francisco,Calif., a corporation of Delaware No Drawing. Application March 23,1937,

Serial No. 132,540

13 Claims. (01. zen-156.5)-

In our copending application, Serial No. 23,521, filed May. 25, 1935, wehave described and claimed a class of cyclic acetals which arecharacterized by the possession of at least one tertiary carbon atomembraced in a heterocyclic ring and linked to an oxygen atom of saidheterocyclic ring. The present invention relates to a practical andeconomical process in accordance with which such cyclic acetals, amongothers, may be converted in practically quantitative yields to valuableglycols possessing at least one tertiary carbinoi group in theirstructure.

The process of the-invention comprises reactinga cyclic acetalpossessing at least one tertiary carbon atom embraced in theheterocyclic ring of the acetal and linked to an oxygen atom. of saidheterocyclic ring with water, preferably with a dilute aqueous acidicsolution, in the presence of sucha hydrogen-ion concentration in thereaction mixture, and at such a temperature, that the cyclic acetal ishydrolyzed to the corresponding glycol containing at least one tertiarycarhinol group at a practical rate while dehydration of the resultingglycol is substantially obviated. The general reaction involved in theprocess of the invention may be illustrated by the following equationrepresenting the reaction of the isobutylene glycol-isobutyraldehydecyclic acetal, a representative cyclic acetal of the class to which theprinciples of the invention are applicable,

ondary glycols. Applicants attempted to utilize the teachings of theprior art to effect the hydrolysis of the members of their novelsubclass of, cyclic acetals containing a tertiary carbon atom embracedin the heterocyclic ring to the 5. valuable glycols containing atertiary carbinol group, that is, the tertiary-primary,tertiary-secondary and tertiary-tertiary glycols. These attempts metwith no success. None of the processes of the art drawn to thehydrolysis of the 10 Instead of the expected equimolecular mixture oi.15

the tertiary carbinol-containing glycol and carbonylic compounds,carbonylic compounds were obtained exclusively. For example, attempts tohydrolyze isobutylene glycol-isobutyraldehyde cyclic acetalto anequimolecular mixture of iso- 2o butylene glycol and isobutyraldehydeunder the conditions of hydrogen ion concentration, temperature,pressure and contact time of the reactants established by the art assuitable for the hydrolysis of the known cyclic acetals resulted in 25complete conversion of the cyclic acetal to isobutyraldehyde. v 1

The reason for the marked differences in behavior of non-tertiary cyclicacetals and the tertiary cyclic acetals appears to be due to the fact 30with water: that whereas the former on reaction with water w arb e-0'cn-onom+mo=cn=.con-oH,0n+oH,-cH-ono 35 inc-0' 011;. cm on,

The cyclic acetal reacts with water to form equimolecular quantities ofthe corresponding glycol possessing a tertiary carbinol group, and a carbonylic compound.

It is known that the cyclic acetals of the stable glycols containingonly primary and/or secondary carbinol groups as ethylene glycol,propylene 5 glycol, alpha-butylene glycol and the likehave been reactedwith water, under acidicyneutral and basic conditions and at roomtemperature and elevated temperatures, and the cyclic acetal hydrolyzedto the corresponding stable primary- 50 primary, secondary-primary orsecondary-secyield non-tertiary glycols which are quite stable understrongly acidic or basic conditions at temperatures at which-thereactionproceeds rapidly, 40

the latter, or tertiarypyclic acetals, on reaction with water yieldtertiary glycols which are very unstable and are completely dehydratedto carbonylic compounds under the acidic conditions and temperaturesfound to be most suitable for the hydrolysis of the non-tertiary cyclicacetals.

Thus, the tertiary cyclic acetals cannot be reacted with water andconverted to the unstable cyclic acetals. I'he non-tertiary glycolsresulting from the hydrolysis of the non-tertiary cyclic acetals of theart are substantially completely stable under stronglybasic and acidicconditions at temperatures sufilciently high to eifect the hydrolysis oftheir cyclic acetals at a practical rate. The tertiary glycols resultingfrom the hydrolysis of the cyclic acetals containing a tertiary carbonatom embraced in the heterocyclic acetal ring are, on the other hand, sounstable and so sensitive as regards the pH value and temperature of thehydrolysis mixture in which they are formed that their preparation bythe cyclic acetal hydrolysis methods of the prior art is impossible. Thecyclic acetals containing a tertiary carbon atom embraced in theheterocyclic ring behave difierently than the cyclic acetals devoid ofsuch a tertiary carbon atom in still other respects. For example, whilethe non-tertiary cyclic acetals can be hydrolyzed in basic solutions,the tertiary cyclic acetals are stable under basic conditions andrequire neutral or acidic conditions for their hydrolysis.

We have discovered that the cyclic acetals containing at least onetertiary carbon atom em' braced in a heterocyclic acetal ring and linkedto an oxygen atom of said ring can be converted to the correspondingglycols containing a tertiary carbinol group in practically quantitativeyield at a practical rate by carefully controlling the pH value andtemperature of the hydrolyzing reac-. tion mixture.

A preferred group of cylic acetals which may be converted to valuableglycols containing at least one tertiary carbinol group in accordancewith the process of the invention is conveniently represented by thegeneral formula wherein at least one of the carbon atoms embraced in theheterocylic ring is tertiary, that is, linked to three carbon atoms, andwherein R, -R1, R2, R3 and R4 represent the same or dlfierentsubstituents of the group consisting of the hydrogen atom and organicradicals. It is seen that, in any case, at least R and R1 or R2 and R4will represent organic radicals. The organic radicals represented by R,R1, R2, R3 and R4 may be hydrocarbon radicals of straight chain,branched chain or cylic character which may or may not be further.substituted by suitable inorganic or organic substituents. For example,R, R1, Ra, R3 and R4 may represent alkyl, alkenyl, aralkyl, aralykenyl,aryl, alicylic and the like radicals one or more hydrogen atoms of whichmay be replaced by substituents as halogen atoms, hydroxy groups, alkoxygroups, aryloxy groups, carboxy groups and the like.

' A preferred subgroup of cylic acetals may be represented by thegeneral formula 'gerein R and R1 represent alkyl radicals which y or maynot be further substituted, and Ra and R3 represent hydrogen atoms oralkyl radi- 'cals which may or may not be further substituted.

The following are representative cylic acetals which may be converted tovaluable glycols containing a tertiary carbinol group in accordance withthe process of the invention:

and the like and their homologues, analogues and suitable substitutionproducts. The cyclic acetals may be treated severally or in admixturewith each other or substantially inert solvents or diluents.

The hydrolysis of the cylic acetal is preferably eflected by treating itwith water or a relatively dilute aqueous solution or suspension of anacid or acid-acting compound at a temperature at which the tertiaryglycol resulting from hydrolysis of the cyclic acetal is substantiallystable. Under conditions at which the products of the hydrolysis aresubstantially stable, an equilibrium exists in the reaction mixturebetween the cyclic acetal and the hydrolysis products. Either one orboth of the hydrolysis products maybe removed from the reaction mixturesubstantially as soon as formed therein, thus speeding up the reactionand forcing it to substantial completion by shifting the equilibrium tothe right. In most cases, the carbonylic. compound formed inequimolecular quantity with the tertiary glycol in the reaction mixtureis an aldehyde. In some cases, particularly when the hydrolysis reactionyields a glycol possessing only secondary, tertiary or secondary andtertiary carbinol groups,

the hydrolysis mixture may contain, in addition to an aldehyde, arelatively small amount of a ketone. This ketone is formed bya'mechanism at present not fully understood. The reaction is preferablyeffected in such an apparatus and under such conditions of temperatureand pressure that the carbonylic compound or compounds may be distilledfrom the reaction mixture. The hydrolysis reaction may be effected atany convenient pressure. When hydrolysis is effected under neutralconditions with water alone, the rate of hydrolysis may be acceleratedby effecting the reaction under pressures greater than atmospheric.

The reaction is preferably effected in the presence of a relativelydilute aqueous acid solution. Excellent results are obtained employingaqueous acidic solutions having a pH value of from about 1 to about 7,and preferably from about 1 to about 3. Aqueous acid solutions having ahydrogen ion concentration of about 0.01N, for example, a sulphuric acisolution having a concentration of about 0.05% by weight of H2504, areconveniently employed. Higher or lower hydrogen ion concentrations canbe used when necessary or desirable dependingupon the particular cyclicacetal hydrolyzed and upon the temperature at which the hydrolysis iseffected. The use of higher acid concentrations is, in general,undesirable since excessive dehydration. of the resulting tertiaryglycol is favored. Furthermore, the tertiaryglycols are moreeasilyrecovered from neutral or slightly basic aqueous solutions.Consequently, the use of the weaker acid'solutions minimizes losses ofacid occasioned by neutralization of the reaction mixture prior torecovery of the glycol therefrom, when resort is had to such a mode ofrecovery.

Suitable acids and acid-acting substances for use in execution of theinvention include the mineral acids, the mineral acid salts and othersubstances capable of forming mineral acids or of acting as mineralacids under the conditions of ,operation and in contact with theconstituents acid and the like.

The temperature at which the hydrolysis is effected will depend to acertain extent upon the particular cyclic acetal to be hydrolyzed andupon the pH value of the reaction mixture. The

reaction temperature is preferably controlled with respect to the pHvalue of the hydrolysis mixture and the pressure so that the hydrolysisis effected at a practical rate under conditions at which the tertiaryglycol is substantially stable and at which the carbonylic compound canbe distilled from the reaction mixture during the hydrolysis reaction. Apreferred temperature range is from about 50 C. to about 125 C. Higheror, lower temperatures may be used when necessary or desirable.

The process may be executed in a batch, intermittent or continuousmanner in any suitable type of apparatus. A preferred type of apparatuscomprises a reaction vessel equipped with means for agitating itscontents as by mechanical stirring or other means, and means fordistilling the carbonylic compound from the reaction mixture duringthehydrolysis reaction.

The tertiary glycol may be recovered from the aqueous hydrolysis mixturein a variety of suitable manners. The glycol may be recovered from theacidic reaction mixture, or the reaction mixture may be made neutral orslightly basic prior to the glycol recovery operation by the additionthereto of the required amount of a neutralizing agent. Suitableneutralizing agents include the basic metal oxides, hydroxides,carbonates, bicarbonates, etc., as well as ammonia, basic ammoniumcompounds, organic bases and the like. The glycol may be recovered fromthe acidic, neutral or basic aqueous reaction mixture by extraction witha suitable selective solvent therefor.

Suitable solvents for this purpose include the water insoluble alcohols,ethers and carboxylic acid esters, in particular the symmetrical andmixed aliphatic ethers. The glycol may be recovered from the extractsolution by distillation under ordinary or reduced pressure. The glycolmay, if desired, be recovered from the reaction mixture, preferablyafter it has been neutralized or made slightlybasic, bydistilling orevaporating water therefrom at atmospheric or reduced pressure until theglycol solution is concentrated to the desired degree. The residue,which will contain the glycol and a salt, may be filtered for removal ofthe solid salt and the filtrate used per se or, if a purer glycol isdesired, the'filtrate may be treated with a suitable selective solvent,and the glycol recovered from the extract solution in a substantiallypure state.

The following specific examples are introduced to illustrate suitablemodes of executing the invention. It is to be understood that theinvention About gm. (0.695 mols) of the cyclic acetal of the formula$113 cm-o-o max m-0H3 mcwo" cm were added to an aqueous sulphuric acidsolution containing about 0.05% of H2804. The mixture was stirred andheated while an azeotropic mixture of isobutyraldehyde and water wasdistilled therefrom at a temperature of about 60 C. The distillation wascontinued until no more aldehyde could be detected in the distillate. Atotal of 49 gm. (0.68 mols) of isobutyraldehyde were distilled from thereaction mixture.

The residue was cooled and neutralized. The distillation was thencontinued until substantially all of the water had been removed. Theresidue contained about 60 gm. (0.67 mols) of isobutylene glycol,representing a yield of about 97% calculated on' the cyclic'acetaltreated.

- Example II ture. An azeotrope of isobutyraldehyde and water wasdistilled from the system at a still-head temperature of about 60 C. Thedistillation was continued until the distillate no longer contained anysubstantial amount of isobutyraldehyde. About 1.673 kgs. (23.24 mols) ofisobutyraldehyde were recovered from the distillate.

The residue was neutralized and the distillation continued untilsubstantially all of the water had been removed. The residue containedabout 1.995 kgs. (22.17 mols) of isobutylene glycol, representing ayield of about 90% on the applied cyclic, acetal.

The glycols prepared in accordance with this invention are valuablematerials for a wide variety of commercial uses. They are useful assolvents and extractants, alone or in admixture with other agents. Theyare useful as components of anti-freeze solutions for use in the coolingsystems of internal combustion engines and for other heat-transferringpurposes. They are also useful as components of preservative solutions,and as starting materials in the production of explosives, resins,ethers, esters, carboxylic acids, aldehydes, ketones, etc.

While we have described our invention in a detailed manner and providedspecific examples illustrating suitable modes of executing the same, itis to be understood that modifications may be made and that nolimitations other than those imposed by the scope of the appended claimsare intended.

This application is a continuation-in-part of our application, SerialNo. 23,521, filed May 25, 1935, which has issued as U. S. Patent2,078,534, dated April 27, 1937.

We claim-as our invention:

1. A process for the production of a polyhydric alcohol containing atleast one tertiary carbinol group which comprises reacting a cyclicacetal containing at least one tertiary carbon atom embraced in theheterocyclic ring and linked to an oxygen atom of said ring with waterin an aqueous medium having a pH of from about 1 to about 7, at atemperature of from about 50 C.

to about 125 C. whereby the cyclic acetal is hydrolyzed toequimolecularquantities of the corresponding polyhydric alcohol and acarbonylic compound, the carbonylic compound being dis tilled from thereaction mixture during the hydrolysis reaction.

2. A process for the production of a glycol containing at least onetertiary carbinol group which comprises reacting a cyclic acetalcontaining at least one tertiary carbon atom embraced in theheterocyclic ring and linked to an oxygen atom of said ring with waterin an aqueous medium having a pH of from about 1 to about 7 at atemperature of from about 50 C. to about 125 C., the carbonylic compoundwhich is formed in substantially equimolecular quantity with the glycolbeing distilled from the reaction mixture during the hydrolysisreaction.

3. A process for the production of a glycol containing at least onetertiary carbinol group which comprises reacting a cyclic acetalcontaining at least-one tertiary carbon atom embraced in theheterocyclic ring and linked to an oxygen atom of said ring with adilute aqueous acidic solution having a pH of from about 1 to about 7,at a temperature of from about 50 C. to about 125 C., and recovering theglycol from the aqueous reaction mixture.

4. A process for the production of a glycol containing at least onetertiary carbinol group which comprises reacting a cyclic acetalcontaining at least one tertiary carbon atom embraced in theheterocyclic ring and linked to an oxygen atom of said ring with anaqueous solution of a mineral acid having a pH value of from about 1 toabout 3 at a temperature of from about 50 C. to about 125 C., andrecovering the glycol from the aqueous hydrolysis mixture.

5. A process for the production of a glycol containing at least onetertiary carbinol group which comprises reacting a cyclic acetalcontaining at least one tertiary carbon atom embraced in theheterocyclic ring and linked to an oxygen atom of said ring with anaqueous solution of a mineral acid having a pH value of from about 1 toabout 3 at a temperature of from about 50 C. to about 125 C., whiledistilling the carbonylic compound, which is formed in a substantiallyequimolecular quantity with the glycol, from the reaction mixture duringthe hydrolysis reaction.

6. A process ior the production of a glycol containing at least onetertiary carbinol group which comprises reacting a cyclic acetalcontaining at least one tertiary carbon atom embraced in theheterocyclic ring and linked to an oxygen atom of said ring with anaqueous sulphuric acid solution having a concentration of about 0.05%H2804 at a temperature greater than about 50 C., and recovering theresulting glycol from the aqueous reaction mixture.

7. A process for the production of a glycol containing a tertiarycarbinol group which comprises reacting a cyclic acetal of the generalformula wherein R and R1 are hydrocarbon radicals, and R2 and R3 aresubstituents of the group consisting of the hydrogen atom andhydrocarbon radicals, with an aqueous acidic solution having a pH valueof from. about 1 to about 3 at a temperature of from about 50 C. toabout 125 C.,

and recovering the glycol from the aqueous reaction mixture.

8. A process for the production of a glycol containing a tertiarycarbinol group which comprises reacting a cyclic acetal of the generalformula HaC-O wherein R and R1 are hydrocarbon radicals, and R3 is asubstituent of the group consisting of the hydrogen atom and hydrocarbonradicals, with an aqueous acidic solution having a pH value of fromabout 1 to about 3 at a temperature of from about 50 C. to about125 C.,and recovering the glycol from the aqueous reaction mixture.

9. A process for the production of a glycol containing a tertiarycarbinol group which comprises reacting a cyclic acetal of the generalformula wherein R and R1 are hydrocarbon radicals, and R2 and R3 aresubstituents of the group consisting of the hydrogen atom andhydrocarbon radicals, withan aqueous solution of a mineral acid having apH value of from about 1 to about 3 at a temperature of from about 50 C.to about 125 C., while distillingthelcarbonylic compound, which isformed in a substantially equimolecular quantity with the glycol, fromthe reaction mixture during the hydrolysis reaction.-

10. A process for the production of a glycol containing a tertiarycarbinol group which comprises reacting a cyclic acetal of the generalformula CHR:

wherein R and R1 are hydrocarbon radicals and R3 is a substituent of thegroup consisting of the hydrogen atom and' hydrocarbon radicals, with anaqueous solution of a mineral acid having a pH value of from about 1 toabout 3 at a temperature of from about 50, C. to about 125 C., whiledistilling the carbonylic compound, which is formed in substantiallyequimolecular quantity with the glycol, from the reaction mixture duringthe hydrolysis reaction.

11. A process for the production of isobutylene glycol which comprisesreacting a cyclic acetal of the general formula GHs--O CH R-a HzC-0wherein R3 is a substituent of the group consisting of the hydrogen atomand hydrocarbon radicals, with an aqueous acidic solution having a pHvalue of from about 1 to about 3 at a temperature of from about 50 C. to125 C., and recovering the isobutylene glycol from the aqueous reactionmixture. 1

12. A process for the production of isobutylene glycol which comprisesreacting the cyclic acetal of the formula with an aqueous acidicsolution having a pH value of from about 1 to about 3 at a temperatureof from about 50 C. to about 125 C., while dis- CHt CHr-( J-O HaC-O CHawith anaqueous sulphuric acid solution containing about 0.05% of HzSO4at a temperature of from about 50 C. to about 125 0., while distillingisobutyraldehyde, which is formed in substantially equimolecularquantity with the isobutylene glycol, from the reaction mixture duringthe hydrolysis reaction.

HERBERT P. A. GROLL. GEORGE HEARNE.

